Method and transaction interface for secure data exchange between distinguishable networks

ABSTRACT

In one embodiment, the present invention includes a method for secure data exchange between an external network and an internal network ( 1  and  2 ) via a transaction interface ( 3 ), in which an external user can undertake predetermined data transactions within the internal network ( 2 ). An interface server ( 7 ) and interface memory ( 11 ) may be coupled between an external network and an internal network. The present invention discloses security techniquest that may be used, including encryption, request processing, and checking. In one embodiment, a first firewall is coupled between the external network and the interface server and a second firewall is coupled between the interface server and the internal network.

The invention relates to a method and transaction interface for secure exchange between distinguishable networks, especially between an external network and an internal network, such as the Internet and a company-owned intranet.

Such methods and devices for secure exchange between networks with mostly different security standards belong to the prior art.

Thus isolation of an internal data network from the external network by a secure interface belongs to the prior art. In the best case, such a secure interface comprises an external server and an internal server, which are in data communication with one another via a firewall. Any customer requests received by the external server are processed in the external server and, after various security checks, are delivered via the firewall to the internal server, which ultimately accesses the data filed within the internal network to be protected.

The firewall disposed between the internal server and external server is supposed to prevent external sources from effecting transactions or changes, especially of improper nature, to the protected database of the internal network.

The actual effect of the firewall is to ensure that external customers lacking appropriate authorization cannot enter into data communication with the internal network and that, if data communication exists, impermissible data such as virus programs cannot be introduced through the firewall into the internal network. Consequently, desired customer service inquiries that are inherently permissible and necessitate internal data transactions are also blocked, for example, for lack of authorization.

A standard solution for this problem comprises opening an additional special customer gateway, which permits appropriate access. This in turn has the disadvantage that attacks on the internal database are now possible via this gateway, even though it is particularly secure.

Another solution leaves all customer questions of any type to the external server, and thus avoids any undesired risky direct data links to external sources. A disadvantage of this solution, however, is that any confidential customer data are temporarily stored on an unprotected external server. For this reason the data are frequently matched by reflection. Because of the resulting greater data volume, this is achieved at the cost of increased processor power, or poorer time response. Moreover, real-time access to the protected database of the internal network is hardly possible in this solution.

A solution to this problem is known from International Application WO 97/19611, in the form of a “security gateway interface” (SGI), which attempts to solve the described problem by providing that, in response to a customer request, authentication of the customer takes place first and, if the customer has the appropriate authorization, the external server then generates its own permissible inquiry on the basis of the customer inquiry. Hereby the data sent by the customer are truly decoupled from the data ultimately intended for further processing. The request generated by the external server is ultimately forwarded via the firewall to an internal server while further security routines are running and finally processed in the internal network, and a response to the user is sent via the external server. Therewith this system ensures complete decoupling of internal and external networks. Nevertheless, the problem remains unsolved that confidential user data still remain on the external server, largely unprotected against access by external sources. If an improper access to the external unprotected server is subsequently successful, some impermissible inquiries can be generated here by sufficiently skilled manipulation. This is possible in particular because authentication of the user inquiry necessarily takes place on the external server and thus in the largely nonsecure area of the system.

The object of the invention is therefore to provide a method and a device for secure data exchange between distinguishable networks that ensures complete decoupling of the two networks and also avoids the cited disadvantages of the already known prior art.

This object is achieved by a method for secure data exchange according to claim 1 and by a transaction interface according to claim 15.

By the fact that, in contrast to the prior art, all inquiries of external users are conditioned by an interface server and stored temporarily in precisely defined form in an interface memory, whereas complete processing of these inquiries including authentication of the user takes place within the secure internal network, no access whatsoever to security-related data areas of the internal network is possible from external sources.

Advantageous improvements of the invention are specified in dependent claims 2 to 14.

According to claim 2, the queue set up in the interface memory is queried exclusively by the internal server at a specified frequency. Accordingly, it is not possible actively to initiate any kind of data transaction in the internal network from an external network, since all actions proceed from the secure area of the internal network and are also initiated from here and ultimately are completely processed here. They also include in particular authentication of the user.

The security level of the method can be further enhanced by using an external firewall between the neutral zone and the external network connected at the front end. Moreover, improper access to data filed in the neutral zone is made more difficult hereby, even if these data are not inherently relevant to security.

In this context a further enhancement of the security standard is achieved by interposing a further internal firewall between the neutral zone and the internal network. The internal firewall also ensures effective protection against espionage from internal sources, or in other words access from the internal network to user data filed in the neutral zone.

The internal firewall enforces exclusively unidirectional communication. In principle, therefore, calls are accepted only from the area of the internal network. A call from the neutral zone into the area of the secure internal network is not possible.

User inquiries can be received in different data formats. For this purpose it may be practical to provide, in the neutral zone, a special external server, which is responsible for specified selected data formats and which first converts the user inquiries received here before forwarding them to the actual interface server and if necessary sends confirmation of receipt to the user.

By the fact that inquiries once received in the queue of the interface server are temporarily stored. resistantly until they have been completely handled, processing can be resumed substantially without data loss even after a complete system crash. In the worst case, processing of the inquiry must be repeated. Hereby the inventive method is robust to the highest degree. This represents a feature of both data security and operator friendliness.

A further performance feature of the inventive method is that the processing speed can be adapted to the respective load. According to claim 7, one way in which this is achieved is by load-dependent control of the frequency of querying of the interface memory.

This can also be achieved advantageously, however, by activation of parallel processes within the interface server and/or the internal server. Load control is then effected with by the external server of the system or by means of a load-control module of the firewall. This is practical because the load controller is hereby positioned at locations disposed in front of the interface server and/or internal server, and thus the necessary processor capacities can be prepared before they are needed. The operator friendliness of the system is also enhanced hereby.

Besides the interconnection and activation of further processes under software control, additional processor activities can also be enabled or disabled by appropriate load control according to claim 10.

The user inquiries filed in the interface memory are advantageously encrypted. The encryption of these inquiries makes access to any confidential user inquiries more difficult not only from outside sources but also from inside sources. Espionage from both external and internal sources is also prevented hereby.

An advantageous encryption method is specified in claim 12. In this connection a special security feature is achieved by the individually predeterminable life of the key used in each case. This means that, even if a hacker were to be successful in decrypting a key being used, it is far from certain that he could achieve a successful improper use or even a data transaction, since the time corridor defined upon allocation of the key is so narrow that an improper second use of the key already appears to be as good as prevented by virtue of its limited life.

A further substantial security feature of the method is that authentication of the respective user takes place separately from the actual processing operation.

An important feature according to claim 14 is that, although authentication of the user takes place completely within the secure area of the internal network, at no time is the respective password allocated to a user sent from the neutral zone into the internal network or in the opposite direction.

The method is advantageously effected with a transaction interface according to independent claim 15.

Further improvements of the inventive device are specified in dependent claims 16 to 29.

According to claim 16 or 17, the security level of the inventive device can be further enhanced by the use of an internal and/or external firewall.

The operator friendliness and scope of application of the transaction interface can be enhanced by an additional external server disposed in the neutral zone.

Dynamic configuration of the transaction interface by constant, preferably periodic and in particular automatic overwriting of the configuration from the secure area of the internal network represents a further security feature, since in this way any improper manipulations of the configuration by unauthorized access from the external network are at worst of short duration and therefore the risk in particular of “stealthy” infiltration is eradicated. It has been proved that slowly building attacks represent a considerably greater risk than immediate and massive attacks, which can also be rapidly detected and dealt with.

Drawing from the same security concept, overwriting of the static data contents of the neutral zone at predeterminable time intervals is also a practical improvement of the invention.

In the inventive transaction interface, better load adaptation of the interface memory itself can also be achieved by appropriate scaling to the respective load.

Better load selection is also achieved by providing a plurality of network computers within the neutral zone.

For the same reason, a plurality of network computers can also be provided in the area of the internal network.

By the fact that the inventive transaction interface is provided with a CORBA interface, different operating systems can work together in the area of the internal network and be protected via the inventive transaction interface.

In a particularly advantageous embodiment, the entire transaction interface is provided with continuous CORBA bus architecture.

Communication within the transaction interface is advantageously processed in encrypted form, preferably encrypted according to DES.

By the fact that, according to claim 25, a confirmation request can be sent to the user before processing of corresponding user inquiries, the transaction interface is capable of correctly closing contracts within the Internet. The repeated confirmation of the user inquiry or of the contract achieved in this way ensures unobjectionable closing of the contract in the area of e-commerce.

The entire operation of the transaction interface is recorded by means of an appropriate logging module within a log. All transactions and items of information, such as the waiting time of the respective user inquiry in the queue, the user ID, etc., are registered in this log.

Hereby it is made possible for an administrator to monitor the operation, to track any malfunctions at an early stage and in particular to detect any attempts at improper use.

The invention will be explained in more detail hereinafter by means of one or more practical examples illustrated only schematically in the drawing, wherein:

FIG. 1 shows a block diagram of the structure of the transaction interface,

FIG. 2 shows a detailed block diagram of the transaction interface,

FIG. 3 shows a flow diagram of the method for secure data exchange, and

FIG. 4 shows a block diagram of the sequence of the method.

FIG. 1 shows an external network 1 and an internal network 2, which can be brought into data communication with one another via a transaction interface 3.

External network 1 is usually the Internet, while internal network 2 can be the intranet of a company, in many cases a LAN. Strictly speaking, transaction interface 3 is not closed between both networks.

In principle, secure data exchange already begins within external network 1 and ultimately leads to transactions within internal network 2, as illustrated by the broken line in FIG. 1.

In addition, transaction interface 3 is provided with an external firewall 4, which insulates a neutral zone 5 from external network 2.

Neutral zone 5 in turn is insulated from internal network 2 by a further internal firewall 6. The arrows illustrated symbolically in FIG. 1 symbolize only the interaction between the mutually separated areas and not anything such as data-flow directions.

As follows from the detailed diagram in FIG. 2, neutral zone 5 comprises an interface server 7 as well as an external server 10. In almost all cases, external server 10 will be a standard web server. Furthermore, an interface memory 11 is provided in the neutral zone, preferably as a constituent of interface server 7. Interface server 7 is in data communication via internal firewall 6 with an internal server 12, which is already disposed within the secure area of internal network 2. Internal server 12 is connected via a CORBA interface 13 to one or more network servers 14 or preferably to distributed database applications 15 via a CORBA bus 16. CORBA bus 16 represents an open bus system, whose purpose is to ensure that the most diverse systems, and therefore also different operating systems, can communicate with one another over this CORBA bus 16.

For example, Unix or Windows operating systems, building-control systems or Sun workstations can be addressed over the same CORBA bus 16.

The said CORBA bus architecture is used in a preferred embodiment for the entire data exchange within transaction interface 3.

The exact sequence of the method for secure data exchange in response to a user inquiry from external network 1, otherwise known as a request, will be explained in detail hereinafter with reference to FIGS. 3 and 4:

Via the hypertext transport protocol of the Internet, an external user 17 can obtain, for example, an HTML form for data exchange with internal network 2. He then has the opportunity to formulate his request within this HTML form. Use of the HTML form is necessary because only predetermined permissible data transactions are possible within the method of secure data exchange described here. In this respect, the use of HTML forms also ensures that only these predetermined inquiries are formulated by external users 17. Via a client interface 20, such as a Java console, the HTML form is then transmitted in encrypted form through the Internet and, if the external user 17 has the appropriate authorizations or passwords, arrives via an external firewall 4 at external server 10, which is located within neutral zone 5. In the case under consideration here, external server 10 is a web server. Within the scope of the invention, transaction interface 3 can also enter into data communication with other data formats, such as RMI. Thus the exchange operation can also be processed from the Internet by means of older browser types or with other network formats.

Such inquiries are then not processed via external server 10, but go directly to interface server 7.

Under these conditions, it is entirely possible for web server 10 to be a processor unit in its own right or a module of interface server 7. It does not absolutely have to be a closed computing unit. In the practical example illustrated in FIG. 4, neutral zone 5 comprises substantially interface server 7, which is provided with an entire series of modules.

The broken lines ending in arrowheads in FIG. 4 denote a call, which initiates an action at the called location, and the solid lines ending in arrowheads represent data flow in the direction of the arrow.

After reception in web server 10, the inquiry received from the Internet 2 is first read in decrypted form and then sent to interface server 7. Interface server 7 is provided with a welcome module 21 for automatic actuation of reception or for welcoming user 17. Before anything else happens, a confirmation of receipt or greeting for external user 17 is returned via web server 10 and external firewall 4 to user 17.

Depending on the inquiry, it is decided at this time, and user 17 is so notified, as to whether the received inquiry will be processed synchronously or asynchronously. In the case of synchronous processing, the external user will obtain the result of his inquiry while still in the same on-line session.

In contrast, in the case of asynchronous processing, the result is sent to the external user only in a subsequent on-line session or in a separate process. The decision as to whether synchronous or asynchronous processing will take place is based on the power and relevance to security of the inquiry received from external user 17.

Interface server 7 now begins to decompose the received request into uncritical data packets and to place it in a queue 22 or 22′, which is located in a special interface memory 11 or 11′, which is also located within neutral zone 5.

At least in the practical example under consideration here, a distinction exists between a queue 22 for authentication of user 17 and a queue 22′ containing the actual inquiry. In the usual situation a single queue but distinguishable memory areas will be provided.

A conventional user inquiry contains the user ID and a password among other particulars. Using the password submitted by user 17 in connection with his inquiry, the user ID is placed in encrypted form in queue 22.

For authentication of user 17, the respective user ID, upon request of internal server 12, is delivered under scrutiny of internal firewall 6 but otherwise in decrypted form to an authentication module 23 in the area of internal network 2.

Within authentication module 23, using the password filed for the respective user ID in the area of internal network 2, the user ID is encrypted and returned in encrypted form via internal firewall 6 to neutral zone 5.

In neutral zone 5, the respective user ID is then decrypted, using the password entered by user 17, by means of an authentication service 24 of interface server 7 implemented in the neutral zone, and the obtained user ID is compared with the temporarily stored user ID.

If the two IDs are identical, processing is continued or enabled, and if not a message to that effect is sent to external user 17.

Before the inquiry received from external user 17 is placed in appropriately conditioned form in queue 22′, verification of the inquiry is performed. Only data records that are semantically correct are placed in the queue. Otherwise processing is aborted and a message to that effect is delivered via web server 10 to external user 17.

Furthermore, a processing log 25 of the currently running processing steps is maintained in neutral zone 5.

Queue 22′ set up in interface memory 11 is checked at regular intervals by internal server 12 for any inquiries that are present and that have yet to be processed.

This ensures that access by external user 17 can under no circumstances initiate any kind of activity within protected internal network 2. Instead, access to the inquiries placed in queue 22′ takes place automatically within internal server 12. This is an important aspect in preventing any manipulations.

If user inquiries that have yet to be processed are detected within queue 22′ in response to a query of queue 22′ effected by internal server 12, they are requested by internal server 12. Before the inquiry is sent to internal server 12, however, the inquiry is first encrypted. This encryption is applied in accordance with the DES method, using a 56-bit key length. Obviously different encryption methods and key lengths can also be used. The keys used are monitored and continuously varied by an encryption management function.

Encryption takes place by means of a basic key, which was created during configuration of the system and which establishes asynchronous SSL encryption. Furthermore, synchronous DES encryption then takes place using this basic key.

In particular, the keys used have only an individually configurable life. This means that a narrow time corridor for secure data exchange is opened upon allocation of the key. After expiration of the life, however, the key can no longer be used, even if an unauthorized person were to succeed in decrypting it. Hereby improper second use of keys is almost precluded.

This new encryption of the inquiry before it is sent to internal server 12 is used primarily to prevent hacking from internal sources, or in other words listening to confidential user inquiries in the area of protected internal network 2.

Hereby the described method additionally prevents espionage from internal sources during secure data exchange. The inquiry encrypted in this way is checked once again as to structure, content and field contents.

If the inquiry now generated proves to be not permissible, further processing is aborted at this location and a message to this effect is sent to external user 17.

If the inquiry is still permissible and therefore corresponds to a predetermined data inquiry or transaction, the inquiry in question is sent via internal firewall 6 of transaction interface 3 to internal server 12. Depending on relevance to security and power, the database inquiry can be processed on one or more servers 12, 12′ or 12″, using one or more database applications 15. Thus all processes relevant to safety are processed in the secure area of internal network 2.

For this purpose the inquiry that has arrived at internal server 12 must first be decrypted before further processing.

After the request has been processed, the result is output and returned in encrypted form via internal firewall 6 to interface server 7. Interface server 7 then performs a “matching check”; in other words a check is run to determine whether the result generated in the area of internal network 2 matches the user inquiry. If this is not the case, an error message is sent to external user 17.

If a match exists, the result is sent to web server 10, converted to a suitable format and then transmitted via external firewall 4 over the Internet 1 to external user 17. Thus a complete data transaction using inventive transaction interface 3 has been described.

Above and beyond this, transaction interface 3 is provided with dynamic load control, which permits adaptation of transaction interface 3 to the respective “traffic”. In addition, as is evident from FIG. 4, load-dependent scaling of interface memory 11′ can be effected on the basis of the traffic. This is illustrated in FIG. 4 by the possible multiple presence of the area denoted by reference symbol 11′.

This means that, depending on the load that is present, interface server 7 arranges the received requests in proper sequence in queue 11 or 11′ and if necessary activates further processes or in other words parallel queues 11′, which can be processed in parallel. For this purpose a plurality of interface servers 7, 7′ or server areas can also be provided within neutral zone 5, to be activated depending on load. This load control is exercised either by web server 10 or by a module of external firewall 4 or by a load-control module 26 of interface server 7.

According to FIG. 6, the load-management function described in the foregoing is advantageously supported by corresponding load control in the area of internal network 2 as well.

Thus, depending on the load that is present, a plurality of internal servers 12, 12′ can be activated or disabled and additional database applications 15 can be activated for processing of the received volume of inquiries in the area of internal network 2.

In this connection it is helpful to provide entire transaction interface 3 with a continuous CORBA bus architecture, so that each inquiry can be allocated to one or more server processes.

For this purpose, internal server 12 acting within internal network 2 is equipped with a CORBA interface 13.

Interior and exterior firewalls 4 and 6 used in the system can be completely conventional software products. In all other respects the CORBA bus permits interconnection of different operating systems such as Windows, NT or Unix within the internal network.

The special architecture of transaction interface 3 described in the foregoing ensures that the minimum requirements applicable in connection with effective closing of contracts in the area of e-commerce are met. For example, a request sent via web server 10 to interface server 7 can first be checked to determine whether it is a contract request. If it is such a request, a contract module set up on interface server 7 can first send a confirmation request to the external user before further processing, after which further processing can take place as described in the foregoing only if this confirmation is received via web server 10.

Above and beyond this, interface server 7 is provided with a logging module, which logs all transactions of transaction interface 3. Hereby all processes can be constantly monitored by an administrator and any malfunctions or attempts at improper use can be detected immediately.

The administrator is located exclusively in the area of internal network 2. Configuration of the transaction interface is possible only from this location.

In this way there is created, for secure data exchange between two distinguishable networks 1, 2, a method and a transaction interface 3 that work with high performance while ensuring complete decoupling of networks 1 and 2, and that make improper use from both external and internal sources seem impossible.

LIST OF REFERENCE SYMBOLS

1 external network

2 internal network

3 transaction interface

4 external firewall

5 neutral zone

6 internal firewall

7 interface server

10 external server

11 interface memory

12, 12′, 12″ internal servers

13 CORBA interface

14 network server

15 database application

17 external user

20 client interface

21 welcome module

22, 22′ queues

23 authentication module

24 authentication service

25 session log

26 load-control module 

1-29. (canceled)
 30. A method of secure data exchange comprising: receiving a request from an external network in a first interface server; comparing the request with a set of permissible requests; storing the request in an interface memory coupled to the first interface server; checking the interface memory exclusively from an internal server; and processing the request in the internal server, wherein the request is processed if the request matches one of the permissible requests and the request is not processed if it does not match one of the permissible requests.
 31. The method of claim 30 wherein the permissible requests have a predefined form and the received request is verified for compliance with the predefined form.
 32. The method of claim 30 wherein the request is received in the first interface server through a firewall.
 33. The method of claim 30 wherein the first interface server is coupled to the internal server through a firewall.
 34. The method of claim 30 wherein communication between the internal server and the first interface server is unidirectional such that calls into the first interface server are only accepted from the internal server and calls into the internal server from the first interface server are not possible.
 35. The method of claim 30 further comprising: generating a processing result in the internal server; sending the result to the first interface server; and determining if the result corresponds to the request.
 36. The method of claim 30 further comprising verifying the semantics of the request.
 37. The method of claim 36 further comprising processing the request in the internal server if the semantics are verified.
 38. The method of claim 30 further comprising authenticating the request and processing the request if the request has been authenticated.
 39. The method of claim 30 wherein the internal server checks the interface memory at regular intervals.
 40. The method of claim 30 wherein the interface memory is scaled based on traffic.
 41. A method of secure data exchange comprising: receiving a request in a first interface server; verifying the request; storing the request in memory if the request is verified; querying the memory using an internal server; and sending the request to the internal server when the request is detected.
 42. The method of claim 41 wherein the memory is queried exclusively from the internal server.
 43. The method of claim 42 wherein the memory is queried at a defined frequency.
 44. The method of claim 41 further comprising: processing the request in the internal server, and in accordance therewith, generating a result; sending the result from the internal server to the first interface server, and determining if the result corresponds to the request.
 45. The method of claim 44 further comprising encrypting the result before sending the result to the first interface server.
 46. The method of claim 41 wherein communication between the internal server and the first interface server is unidirectional such that calls into the first interface server are only accepted from the internal server and calls into the internal server from the first interface server are not possible.
 47. The method of claim 41 further comprising encrypting the request before sending the request to the internal server.
 48. The method of claim 47 wherein encrypting is synchronous.
 49. The method of claim 47 wherein encrypting is asynchronous.
 50. The method of claim 47 wherein encrypting uses a key that expires after a period of time.
 51. The method of claim 47 wherein encrypting uses a key that is continuously varied.
 52. The method of claim 47 wherein encrypting uses a key that has an individually configurable life so that a narrow time corridor for secure data exchange is opened upon allocation of the key.
 53. The method of claim 47 further comprising decrypting the request on the internal server.
 54. The method of claim 41 wherein the request is sent to the internal server if the request corresponds to a predetermined transaction.
 55. The method of claim 41 wherein verifying the request comprises verifying the semantics of the request.
 56. The method of claim 41 wherein the request is received in the first interface server through a firewall.
 57. The method of claim 41 wherein the request is sent from the first interface server to the internal server through a firewall.
 58. A method of secure data exchange comprising: receiving a user-ID and a first password in a first computer system; sending the received user-ID to a second computer system through a first firewall; accessing a second password in the second computer system using the user-ID; encrypting the user-ID in the second computer system using the second password to produce an encrypted user-ID; sending the second encrypted user-ID to the first computer system through the first firewall; decrypting the encrypted user-ID using the first password to produce a first result; and comparing the first result to the received user-ID, wherein processing is enabled if the first result matches the received user-ID.
 59. The method of claim 58 wherein communication between the first computer system and the second computer system is unidirectional.
 60. The method of claim 58 wherein the user-ID and password are received from an external network through a second firewall.
 61. The method of claim 58 wherein the user-ID and password are stored in an interface memory, and the interface memory is queried exclusively by the second computer system.
 62. A secure data exchange system comprising: a first interface server; an interface memory coupled to the first interface server; a first firewall coupled between the first interface server and an external network; s second firewall coupled between the first interface server and an internal network.
 63. The system of claim 62 wherein communication between the internal server and the first interface server is unidirectional.
 64. The system of claim 63 wherein calls into the first interface server are only accepted from the internal server and calls into the internal server from the first interface server are not possible.
 65. The system of claim 62 wherein a request is received in the first interface server through the first firewall and the semantics of the request are verified.
 66. The system of claim 65 wherein the request is stored in the interface memory if the request is verified.
 67. The system of claim 66 wherein the request is stored in the interface memory in encrypted form.
 68. The system of claim 62 wherein the interface memory is interrogated exclusively from the internal network for requests received from the external network.
 69. The system of claim 62 further comprising a second server coupled to the first interface server, wherein the second server converts requests received from the external network and forwards the results to the first interface server.
 70. The system of claim 69 wherein the second server is a web server.
 71. The system of claim 69 wherein the second server sends a confirmation of receipt of requests.
 72. The system of claim 62 further comprising a load control module for scaling the interface memory based on traffic.
 73. The system of claim 62 further comprising a logging module for logging transactions in the first interface server.
 74. A method of secure data exchange comprising: means for receiving a request from an external network in a neutral zone; means for comparing the request with a set of permissible requests; means for storing the request in the neutral zone; means for checking for stored requests exclusively from an internal network; and means for processing the request in the internal network.
 75. The system of claim 74 further comprising means for authenticating requests received from the external network. 